Poly-2-pyrrolidone is the source of a useful synthetic fiber for the textile industry. The melt-spinnable white solid polymer is produced by the alkaline-catalyzed polymerization of 2-pyrrolidone in the presence of carbon dioxide (see U.S. Pat. No. 3,721,652). Polypyrrolidone so-produced is melt-spun into filaments by extrusion from multi-hole spinnerets. In melt-spinning, the polymer composition is extruded in a molten condition at a temperature which is generally greater than about 270.degree. C, and extruder temperatures, i.e., extruder screw barrel temperatures, of about 280.degree. C and higher. The extrusion must be carried out with care because of the tendency of the polymer to thermally degrade and revert to monomer. Degradation produces an unacceptable extrudate containing foam or bubbles. If extrusion is attempted at an appreciably lower temperature to avoid thermal decomposition, or at higher extruder screw rpm to decrease the residence time at the extruder temperature, excessive torque must be developed in the extruder screw, the screw barrel temperature increases further, and the pressure at the spinneret increases and may fluctuate to yield an inconsistent product. Consequently, in order to melt extrude polypyrrolidone efficiently, one may either seek to increase the thermal stability of the polymer, or to improve the extrudability of the polymeric composition, by the use of additives.